I receive emails with this question quite frequently. I am posting my standard answer as it may save some folks time in contacting me and getting a reply if you have the same question.

Question:

I am [name omitted], and I have read your tutorial about converting scanned maps to DEM. I need a DEM for my thesis but I do not know much about it and I really don't know what to do. I already convert the scanned topographical map to a shape file and I cannot afford the license of the program that will convert it to DEM... etc.

I have a government client interested in contours/ medium(or high resolution) elevation data for [some country]. Iíve checked in with a couple of my partners who provide this type of information but am not really coming up with anything presently. Any suggestions are welcome... etc.

Answer:

I recommend considering, SRTM DEM data that is available for most of the earth at a resolution of 90m. One free source is the CGIAR website . ASTER DEM data is also available for most of the earth at 30m resolution. You can download it from the NASA WIST site also free.

If you need higher resolution, you can purchase SPOT DEM data but it is expensive. Making your own DEMs from topographic maps is a very difficult, time consuming process and I recommend against it unless you have no other choice.